土壤水势测定方法的选择及准确性研究

Preliminary study on selection and accuracy of different methods for measurement of soil water potential

通过对土壤水势常用的3种测定方法探讨,发现测定土壤水势的方法存在差别,压力膜的准确度为最高,其次是离心机,张力计的准确度较低。压力膜测定土壤水分特征曲线的形状与原状土壤的特征曲线大致相符,但要完整地测出某土壤的特征曲线需要长达半年之久。离心机测定土壤水分特征曲线较压力膜测定有偏离,离心机测定过程中土壤容重的不断变化、土壤温度升高等造成测定结果有差异,但它的测定周期短。张力计广泛应用于确定农田灌溉的时期,虽然张力计测定结果较差,但它仍是农业生产和实验室测定土壤水势切实可用的仪器,若使用压力传感器保持平衡,对土壤和张力计之间水分交换忽略不计,准确性会显著提高。

The study on three commonly used measurement methods for soil water potential shows that the accurate degree of pressure film is the highest,centrifuge is the second,while tensiometer is the lowest.The soil water characteristic curve results from the measurement of pressure film is almost in conformity with that of the origin one,but it takes as long as half a year to determin completely the characteristic curve.To determin soil water characteristic curve with centrifuge may result in deviation compared with pressure film.The continuous change of soil bulk density and rise of soil temperature in the process of te measurement cause differences in the result,but its measurement period is shorter.The tensometer is extensively applied to determine the time of farmland irrigation.Though its result is not accurate enough,it is still a practicable instrument to measure soil potential in agricultural production and laboratory.If a preasure sensor is used to hold the balance and the swap of moisture between soil and the tensiometer cup is ignored,the accuracy will show an exaltation.